diff --git a/llvm/cmake/config-ix.cmake b/llvm/cmake/config-ix.cmake
--- a/llvm/cmake/config-ix.cmake
+++ b/llvm/cmake/config-ix.cmake
@@ -114,18 +114,20 @@
   set(LLVM_PTHREAD_LIB ${CMAKE_THREAD_LIBS_INIT})
 endif()
 
+if(LLVM_ENABLE_ZLIB)
+  if(LLVM_ENABLE_ZLIB STREQUAL FORCE_ON)
+    find_package(ZLIB REQUIRED)
+  elseif(NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
+    find_package(ZLIB)
+  else()
+    set(ZLIB_FOUND FALSE)
+  endif()
+  set(LLVM_ENABLE_ZLIB "${ZLIB_FOUND}")
+endif()
+
 # Don't look for these libraries if we're using MSan, since uninstrumented third
 # party code may call MSan interceptors like strlen, leading to false positives.
 if(NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
-  if(LLVM_ENABLE_ZLIB)
-    if(LLVM_ENABLE_ZLIB STREQUAL FORCE_ON)
-      find_package(ZLIB REQUIRED)
-    else()
-      find_package(ZLIB)
-    endif()
-    set(LLVM_ENABLE_ZLIB "${ZLIB_FOUND}")
-  endif()
-
   # Don't look for these libraries on Windows.
   if (NOT PURE_WINDOWS)
     # Skip libedit if using ASan as it contains memory leaks.
@@ -164,8 +166,6 @@
       endif()
     endif()
   endif()
-else()
-  set(LLVM_ENABLE_ZLIB FALSE)
 endif()
 
 if (LLVM_ENABLE_LIBXML2 STREQUAL "FORCE_ON" AND NOT LLVM_LIBXML2_ENABLED)